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1. Field of the Invention
The present invention generally relates to neurofeedback equipment and techniques. More particularly, the invention relates to the use of color in a neurofeedback system.
2. Background Information
For many years, neurologists, psychotherapists, researchers, and other health care professionals have studied the human brain. One commonly studied parameter is the electrical activity of the brain. Using electrodes adhered to a person""s scalp in conjunction with associated electronics (amplifiers, filters, etc.), an electroencephalogram (xe2x80x9cEEGxe2x80x9d) is recorded over a given time period depicting the electrical activity of the brain at the various electrode sites. In general, EEG signals (colloquially referred to as xe2x80x9cbrain wavesxe2x80x9d) have been studied in an effort to determine relationships between frequencies of electrical activity or neural discharge patterns of the brain and corresponding mental, emotional and cognitive states. As a result of this type of work, it has become generally accepted that monitoring a person""s EEG and providing feedback information to the person as a function of the EEG can actually serve to enable a person to voluntarily reach or maintain a target mental state and enhance performance in certain areas. This type of feedback technique is referred to generally as xe2x80x9cneurofeedback.xe2x80x9d
As a function of time, EEG signals appear to the untrained eye as seemingly random squiggles on a paper chart or display. Upon more careful inspection, the EEG signals typically follow a pattern of sorts, with peaks and valleys crudely approximating a sinusoidal waveform. The number of peaks of an EEG per second is referred to as the xe2x80x9cfrequencyxe2x80x9d and is measured in units of Hertz (xe2x80x9cHzxe2x80x9d). The frequency of EEG signals vary from site to site on the head, and also vary as a function of the mental state of the person.
A standard has been used for many years to permit easy reference to EEG frequencies. Table I below shows eight standardized frequency bands and the typical mental state associated with each band.
More recently, practitioners have referred less often to the frequency bands by their Greek labels and more often to numerical range of the band (e.g., the xe2x80x9c1-3 Hzxe2x80x9d band). This is largely a result of many practitioners delineating the frequency bands differently.
Numerous neurofeedback techniques have been attempted over the years. Common to many of these techniques is the use of discrete visual or audible feedback signals or cues that relate in some predetermined manner to the person""s EEG signals. These techniques typically compare the frequency of an EEG signal to a predetermined frequency threshold or frequency range and provide one visual feedback signal if the EEG frequency is within the range and a different feedback signal if the frequency is outside the range. The person being trained uses these feedback signals to modify the electrical activity of one or more areas of the brain thereby achieving a target mental state. Examples of such techniques are described in U.S. Pat. Nos. 5,024,235 and 5,899,867.
Although satisfactory to some degree in certain applications, such techniques are generally self-limiting in their ability to display the full range of frequencies at a wide variety of cortical sites in an intuitively easy to understand format. For example, in FIGS. 14-18 of U.S. Pat. No. 5,899,867 (U.S. Pat. No. 5,899,867 incorporated herein by reference in its entirety), a simplistic facial image is shown as the feedback image to the person. The face has two eyes, two eyebrows, a nose and a mouth. The mouth is controlled by the amplitude of the alpha waves (8-12 Hz), and the eyebrows are controlled by the theta wave (4-7 Hz) amplitude. As a form of neurofeedback therapy, this type of visual representation can be difficult for a patient to reconcile and process in a useful manner. Moreover, conventional feedback techniques typically require more of a conscious effort to focus on the task at hand and learn the format for very narrow control.
Additionally, conventional electrodes that are adhered to a person""s scalp for neurofeedback therapy typically use a sticky conductive paste that is messy to apply and messy to clean up afterwards. Further, the time required to correctly position the electrodes and verify that a sufficiently low impedance exists between each electrode and the scalp is relatively long, and the process is generally inconvenient to the person being monitored.
Accordingly, an improved neurofeedback technique is needed, particularly one that avoids or minimizes the feedback issues noted above and the mess and inconvenience involved with adhesive-type electrodes.
The problems noted above are solved in large part by a neurofeedback technique and apparatus that uses color as its feedback cue, and preferably that employ non-adhesive sensors. A preferred embodiment of the invention includes an amplifier that receives EEG or magnetoencephalogram (xe2x80x9cMEGxe2x80x9d) signals from electrodes on or adjacent to the person""s scalp, a low or band pass filter, a color processor and a display unit. The color processor converts an aspect of one or more channels of the person""s EEG signal(s) to a color and shows that color to the person on the display. The aspect of the EEG that is converted to color can be the frequency or the amplitude of the person""s EEG signal(s). If EEG amplitude is used in the conversion process, the instantaneous, average or peak amplitude can be used. This process is dynamic, meaning that the system repeatedly converts the EEG signal to color while the person is receiving neurofeedback training.
By using color as the feedback signal, a plurality (theoretically, an infinite number) of feedback signals can be provided to the user during a feedback session. This is in contrast to many conventional feedback systems which simply inform the person whether, or not, the frequency of the EEG is within a single predetermined frequency range. Also, color-based neurofeedback signal is generally much easier to understand and follow than many types of feedback images heretofore known.
In addition to, or instead of, color, audio can be used as a feedback signal. For example, one audio tone can be generated to inhibit a person""s neuro response and another tone can be used to reward a different response.
The display unit used to provide the color-based feedback information to the user can be a single, stand-alone display (e.g., computer display). Alternatively, the display unit may comprise a pair of displays, one for each eye, such as in the form of head worn goggles. With a pair of displays, the color processor can provide the same or different images and colors to each eye of the person being trained. This provides considerable flexibility in the type of neurofeedback training scenarios the person being trained or a health care professional might desire.
The neurofeedback system described herein may use conventional electrodes that adhere to a person""s scalp with conductive paste. Alternatively, however, the system may use EEG sensors that do not require conductive paste. This latter type of sensor generally detects the electromagnetic energy emanating from a point or area associated with a person""s brain and does not directly contact the person""s scalp, at least not to the same extent as is generally required for conventional adhesive electrodes. One suitable type of non-adhesive sensor is the Superconducting Quantum Interference Device (xe2x80x9cSQUIDxe2x80x9d).
The system described herein advantageously uses color as its feedback information to provide an enhanced neurofeedback experience. Many aspects of the system are fully programmable, such as specifying the EEG channels to be monitored, the colors to be used, whether frequency or amplitude is to be converted to color, etc. Further, the system may use conventional electrodes (which use conductive paste to adhere the electrode to a person""s scalp) or non-adhesive sensors which avoid the use of the paste and minimize the mess and time involved with adhesive electrodes. These and other advantages and benefits will become apparent upon reviewing the following disclosure.